The invention relates to the retrieval of a set of textual records from a database and in particular to the retrieval of such records based on category structures.
It is well known to retrieve information stored in computer databases. In the SMART information retrieval system, described in "Introduction to Modern Information Retrieval, The SMART and SIRE Experimental Retrieval Systems", by Gerald Salton and Michael McGill, McGraw-Hill, New York, 1983, pages 118-156, information is retrieved based on measures of similarity between documents searched and a given query.
It is also known to perform ongoing electronic searches, in which documents in a database are periodically searched for certain words or queries. For example, a company might want to track news items mentioning its name or the name of competing companies.